There is a critical need to quantify and predict the likelihood of Environmental Stress Cracking (ESC) in medical devices, due to the expanding use of medical cleaners in hospitals to prevent infection as well as increased FDA documentation requirements. This paper performs constant flexural strain ESC experiments on two high performance resins, Noryl 20%gf and Ultem 20%gf, using three common hospital cleaners (bleach, quaternary amine with isopropanol, and hydrogen peroxide). ESC testing was performed using a 7-day soak followed by tensile testing to assess residual stress-strain performance.
From strain-at-break results for this 7-day soak method, ratings were obtained for each resin-cleaner combination. These results can be fed into mechanical models of components to quantify likely failure locations and safety factors.
Using time-to-crack datasets, an initial estimate of the n exponent for the ESC dependence on stress was obtained. Also, it was found that the use of Hansen Solubility Parameters could, with reasonably accuracy, predict trends in ESC damage.
Klein, R.J., Gibler, M.J., Jacobs, R.M., Sell, E.L., Lince, S.D. “Environmental Stress Cracking of Medical Thermoplastics: Assessing Lifetime of High Performance Amorphous Resins in Presence of Hospital Cleaners,” ANTEC2016-P063, Proceedings of the ANTEC 2016, Indianapolis, IN, May 23 – 25, 2016.